Acne occurs in greater than 90% of the population at some point in their lives. Although it is primarily considered a disorder of the teenage years, many people (and especially females) suffer from acne during adulthood. Acne (also known as acne vulgaris) is a long-term skin condition that is caused by: 1) plugging of hair follicles by abnormally keratinized cells, 2) microbial colonization of the follicle, 3) inflammation, and 4) increased oil production associated with circulating hormones.
Photoaging occurs naturally as our skin is exposed to the sun's ultraviolet rays, and the first signs of photoaging (including fine wrinkles and hyperpigmentation) typically appear between the ages of 20 and 35. While sun protection is key to minimizing photoaging, there are also various topical treatments which have proven to be efficacious for treating and preventing photoaging.
The desire to treat acne commonly coexists with the desire to treat and/or prevent photoaging. While the application of multiple dermatologic products is an option currently employed by many patients, the existence of a single, efficacious, stable composition would offer benefits in convenience and adherence.
There are numerous difficulties in formulating a single, efficacious, stable composition to treat or prevent acne and photoaging.
First, the successful treatment of acne alone typically involves using two different agents with complementary mechanisms of action. The most common categories are comedolytics (which help keratinization and thus prevent clogged pores) and antimicrobials (which generally target the acne-causing bacterium Propionibacterium acnes or P. acnes). So, the successful treatment of acne and photoaging together would typically require three or more active ingredients, which may require different vehicles, different frequencies of application, and different methods of application.
A second difficulty inherent in creating a combined formulation is that many anti-acne ingredients inactivate other anti-acne ingredients. For example, benzoyl peroxide inactivates tretinoin, erythromycin, and hydroquinone; tretinoin inactivates erythromycin; and benzoyl peroxide can lead to oxidation of zinc pyrithione. There are likely to be many more similar interactions that are not yet described in the dermatology literature.
When it is desired to use anti-photoaging ingredients in addition to anti-acne ingredients, additional interactions arise. When a patient is using benzoyl peroxide (for acne) they should avoid using it at the same time as hydroquinone (used for short-term treatment of photoaging), as the combination can lead to staining of the skin. As another example, niacinamide (a vitamin B3 derivative that can be used as an anti-acne ingredient and as an anti-photoaging ingredient) should not be used with ascorbic acid (the naturally occurring form of vitamin C), as the former can inactivate the latter ingredient. In addition, many photoaging treatments cannot be used long-term because they contain steroids or a bleaching agent (hydroquinone) with potential undesirable side effects.
Thus, for patients receiving treatment for both acne and photoaging, their treatments typically do not come in the same formulation, and additionally, the patients are often instructed to use their individual formulations at different times of day, significantly decreasing the convenience of treatment.
An additional difficulty in formulating a once-daily composition for the treatment of acne and photoaging is that the majority of ingredients for each of these purposes are typically applied to the skin twice daily. These ingredients that are typically applied twice daily include clindamycin, azelaic acid, dapsone, adapalene, benzoyl peroxide, erythromycin, hydroquinone, niacinamide, ascorbic acid, magnesium ascorbyl phosphate, zinc pyrithione, and others. Even for treatment of acne alone, once-daily treatments are not yet the norm because of the potential inactivation of one anti-acne compound by another anti-acne compound and using two different agents with different mechanisms of action often requiring different formulations.
Finally, a method to treat both acne and photoaging would require a collection of active ingredients that are stable and efficacious in the same vehicle. In formulating a vehicle of inactive ingredients to use along with active ingredient(s), one must account for texture, color, scent, method of application, pH, water solubility, alcohol solubility, stability of the active ingredients, and the presence or absence of interactions between the active ingredient(s) and the inactive ingredients. Thus for acne and photoaging to both be treated with a single treatment is a significant advance over most current methodologies. A once-daily composition and method of treatment would be desirable because a once-daily composition increases patient adherence and lowers cost.